21535121 has 2 divisors, whose sum is σ = 21535122. Its totient is φ = 21535120.

The previous prime is 21535093. The next prime is 21535123. The reversal of 21535121 is 12153512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20611600 + 923521 = 4540^2 + 961^2 .

It is a cyclic number.

It is not a de Polignac number, because 21535121 - 2¹⁴ = 21518737 is a prime.

It is a super-2 number, since 2×21535121² = 927522872969282, which contains 22 as substring.

Together with 21535123, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21535093 and 21535102.

It is not a weakly prime, because it can be changed into another prime (21535123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767560 + 10767561.

It is an arithmetic number, because the mean of its divisors is an integer number (10767561).

Almost surely, 2^21535121 is an apocalyptic number.

It is an amenable number.

21535121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21535121 is an equidigital number, since it uses as much as digits as its factorization.

21535121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 300, while the sum is 20.

The square root of 21535121 is about 4640.5948972088. The cubic root of 21535121 is about 278.2162155215.

Adding to 21535121 its reverse (12153512), we get a palindrome (33688633).

The spelling of 21535121 in words is "twenty-one million, five hundred thirty-five thousand, one hundred twenty-one".